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/* Primitive operations on Lisp data types for GNU Emacs Lisp interpreter.
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   Copyright (C) 1985,86,88,93,94,95,97,98,99, 2000, 2001
   Free Software Foundation, Inc.
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This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING.  If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */
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#include <config.h>
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#include <signal.h>
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#include <stdio.h>
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#include "lisp.h"
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#include "puresize.h"
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#include "charset.h"
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#include "buffer.h"
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#include "keyboard.h"
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#include "frame.h"
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#include "syssignal.h"
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#ifdef STDC_HEADERS
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#include <float.h>
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#endif
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/* If IEEE_FLOATING_POINT isn't defined, default it from FLT_*. */
#ifndef IEEE_FLOATING_POINT
#if (FLT_RADIX == 2 && FLT_MANT_DIG == 24 \
     && FLT_MIN_EXP == -125 && FLT_MAX_EXP == 128)
#define IEEE_FLOATING_POINT 1
#else
#define IEEE_FLOATING_POINT 0
#endif
#endif

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/* Work around a problem that happens because math.h on hpux 7
   defines two static variables--which, in Emacs, are not really static,
   because `static' is defined as nothing.  The problem is that they are
   here, in floatfns.c, and in lread.c.
   These macros prevent the name conflict.  */
#if defined (HPUX) && !defined (HPUX8)
#define _MAXLDBL data_c_maxldbl
#define _NMAXLDBL data_c_nmaxldbl
#endif

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#include <math.h>

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#if !defined (atof)
extern double atof ();
#endif /* !atof */

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Lisp_Object Qnil, Qt, Qquote, Qlambda, Qsubr, Qunbound;
Lisp_Object Qerror_conditions, Qerror_message, Qtop_level;
Lisp_Object Qerror, Qquit, Qwrong_type_argument, Qargs_out_of_range;
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Lisp_Object Qvoid_variable, Qvoid_function, Qcyclic_function_indirection;
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Lisp_Object Qcyclic_variable_indirection, Qcircular_list;
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Lisp_Object Qsetting_constant, Qinvalid_read_syntax;
Lisp_Object Qinvalid_function, Qwrong_number_of_arguments, Qno_catch;
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Lisp_Object Qend_of_file, Qarith_error, Qmark_inactive;
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Lisp_Object Qbeginning_of_buffer, Qend_of_buffer, Qbuffer_read_only;
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Lisp_Object Qtext_read_only;
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Lisp_Object Qintegerp, Qnatnump, Qwholenump, Qsymbolp, Qlistp, Qconsp;
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Lisp_Object Qstringp, Qarrayp, Qsequencep, Qbufferp;
Lisp_Object Qchar_or_string_p, Qmarkerp, Qinteger_or_marker_p, Qvectorp;
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Lisp_Object Qbuffer_or_string_p, Qkeywordp;
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Lisp_Object Qboundp, Qfboundp;
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Lisp_Object Qchar_table_p, Qvector_or_char_table_p;
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Lisp_Object Qcdr;
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Lisp_Object Qad_advice_info, Qad_activate_internal;
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Lisp_Object Qrange_error, Qdomain_error, Qsingularity_error;
Lisp_Object Qoverflow_error, Qunderflow_error;

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Lisp_Object Qfloatp;
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Lisp_Object Qnumberp, Qnumber_or_marker_p;

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static Lisp_Object Qinteger, Qsymbol, Qstring, Qcons, Qmarker, Qoverlay;
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static Lisp_Object Qfloat, Qwindow_configuration, Qwindow;
Lisp_Object Qprocess;
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static Lisp_Object Qcompiled_function, Qbuffer, Qframe, Qvector;
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static Lisp_Object Qchar_table, Qbool_vector, Qhash_table;
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static Lisp_Object Qsubrp, Qmany, Qunevalled;
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static Lisp_Object swap_in_symval_forwarding P_ ((Lisp_Object, Lisp_Object));
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int most_positive_fixnum, most_negative_fixnum;

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void
circular_list_error (list)
     Lisp_Object list;
{
  Fsignal (Qcircular_list, list);
}


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Lisp_Object
wrong_type_argument (predicate, value)
     register Lisp_Object predicate, value;
{
  register Lisp_Object tem;
  do
    {
      if (!EQ (Vmocklisp_arguments, Qt))
	{
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	 if (STRINGP (value) &&
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	     (EQ (predicate, Qintegerp) || EQ (predicate, Qinteger_or_marker_p)))
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	   return Fstring_to_number (value, Qnil);
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	 if (INTEGERP (value) && EQ (predicate, Qstringp))
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	   return Fnumber_to_string (value);
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	}
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      /* If VALUE is not even a valid Lisp object, abort here
	 where we can get a backtrace showing where it came from.  */
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      if ((unsigned int) XGCTYPE (value) >= Lisp_Type_Limit)
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	abort ();

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      value = Fsignal (Qwrong_type_argument, Fcons (predicate, Fcons (value, Qnil)));
      tem = call1 (predicate, value);
    }
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  while (NILP (tem));
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  return value;
}

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void
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pure_write_error ()
{
  error ("Attempt to modify read-only object");
}

void
args_out_of_range (a1, a2)
     Lisp_Object a1, a2;
{
  while (1)
    Fsignal (Qargs_out_of_range, Fcons (a1, Fcons (a2, Qnil)));
}

void
args_out_of_range_3 (a1, a2, a3)
     Lisp_Object a1, a2, a3;
{
  while (1)
    Fsignal (Qargs_out_of_range, Fcons (a1, Fcons (a2, Fcons (a3, Qnil))));
}

/* On some machines, XINT needs a temporary location.
   Here it is, in case it is needed.  */

int sign_extend_temp;

/* On a few machines, XINT can only be done by calling this.  */

int
sign_extend_lisp_int (num)
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     EMACS_INT num;
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{
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  if (num & (((EMACS_INT) 1) << (VALBITS - 1)))
    return num | (((EMACS_INT) (-1)) << VALBITS);
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  else
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    return num & ((((EMACS_INT) 1) << VALBITS) - 1);
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}

/* Data type predicates */

DEFUN ("eq", Feq, Seq, 2, 2, 0,
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  "Return t if the two args are the same Lisp object.")
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  (obj1, obj2)
     Lisp_Object obj1, obj2;
{
  if (EQ (obj1, obj2))
    return Qt;
  return Qnil;
}

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DEFUN ("null", Fnull, Snull, 1, 1, 0, "Return t if OBJECT is nil.")
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  (object)
     Lisp_Object object;
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{
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  if (NILP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("type-of", Ftype_of, Stype_of, 1, 1, 0,
  "Return a symbol representing the type of OBJECT.\n\
The symbol returned names the object's basic type;\n\
for example, (type-of 1) returns `integer'.")
  (object)
     Lisp_Object object;
{
  switch (XGCTYPE (object))
    {
    case Lisp_Int:
      return Qinteger;

    case Lisp_Symbol:
      return Qsymbol;

    case Lisp_String:
      return Qstring;

    case Lisp_Cons:
      return Qcons;

    case Lisp_Misc:
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      switch (XMISCTYPE (object))
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	{
	case Lisp_Misc_Marker:
	  return Qmarker;
	case Lisp_Misc_Overlay:
	  return Qoverlay;
	case Lisp_Misc_Float:
	  return Qfloat;
	}
      abort ();

    case Lisp_Vectorlike:
      if (GC_WINDOW_CONFIGURATIONP (object))
	return Qwindow_configuration;
      if (GC_PROCESSP (object))
	return Qprocess;
      if (GC_WINDOWP (object))
	return Qwindow;
      if (GC_SUBRP (object))
	return Qsubr;
      if (GC_COMPILEDP (object))
	return Qcompiled_function;
      if (GC_BUFFERP (object))
	return Qbuffer;
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      if (GC_CHAR_TABLE_P (object))
	return Qchar_table;
      if (GC_BOOL_VECTOR_P (object))
	return Qbool_vector;
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      if (GC_FRAMEP (object))
	return Qframe;
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      if (GC_HASH_TABLE_P (object))
	return Qhash_table;
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      return Qvector;

    case Lisp_Float:
      return Qfloat;

    default:
      abort ();
    }
}

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DEFUN ("consp", Fconsp, Sconsp, 1, 1, 0, "Return t if OBJECT is a cons cell.")
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  (object)
     Lisp_Object object;
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{
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  if (CONSP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("atom", Fatom, Satom, 1, 1, 0,
       "Return t if OBJECT is not a cons cell.  This includes nil.")
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  (object)
     Lisp_Object object;
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{
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  if (CONSP (object))
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    return Qnil;
  return Qt;
}

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DEFUN ("listp", Flistp, Slistp, 1, 1, 0,
       "Return t if OBJECT is a list.  This includes nil.")
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  (object)
     Lisp_Object object;
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{
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  if (CONSP (object) || NILP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("nlistp", Fnlistp, Snlistp, 1, 1, 0,
       "Return t if OBJECT is not a list.  Lists include nil.")
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  (object)
     Lisp_Object object;
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{
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  if (CONSP (object) || NILP (object))
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    return Qnil;
  return Qt;
}

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DEFUN ("symbolp", Fsymbolp, Ssymbolp, 1, 1, 0,
       "Return t if OBJECT is a symbol.")
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  (object)
     Lisp_Object object;
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{
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  if (SYMBOLP (object))
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    return Qt;
  return Qnil;
}

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/* Define this in C to avoid unnecessarily consing up the symbol
   name.  */
DEFUN ("keywordp", Fkeywordp, Skeywordp, 1, 1, 0,
       "Return t if OBJECT is a keyword.\n\
This means that it is a symbol with a print name beginning with `:'\n\
interned in the initial obarray.")
  (object)
     Lisp_Object object;
{
  if (SYMBOLP (object)
      && XSYMBOL (object)->name->data[0] == ':'
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      && SYMBOL_INTERNED_IN_INITIAL_OBARRAY_P (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("vectorp", Fvectorp, Svectorp, 1, 1, 0,
       "Return t if OBJECT is a vector.")
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  (object)
     Lisp_Object object;
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{
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  if (VECTORP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("stringp", Fstringp, Sstringp, 1, 1, 0,
       "Return t if OBJECT is a string.")
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  (object)
     Lisp_Object object;
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{
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  if (STRINGP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("multibyte-string-p", Fmultibyte_string_p, Smultibyte_string_p,
       1, 1, 0, "Return t if OBJECT is a multibyte string.")
  (object)
     Lisp_Object object;
{
  if (STRINGP (object) && STRING_MULTIBYTE (object))
    return Qt;
  return Qnil;
}

DEFUN ("char-table-p", Fchar_table_p, Schar_table_p, 1, 1, 0,
       "Return t if OBJECT is a char-table.")
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  (object)
     Lisp_Object object;
{
  if (CHAR_TABLE_P (object))
    return Qt;
  return Qnil;
}

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DEFUN ("vector-or-char-table-p", Fvector_or_char_table_p,
       Svector_or_char_table_p, 1, 1, 0,
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       "Return t if OBJECT is a char-table or vector.")
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  (object)
     Lisp_Object object;
{
  if (VECTORP (object) || CHAR_TABLE_P (object))
    return Qt;
  return Qnil;
}

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DEFUN ("bool-vector-p", Fbool_vector_p, Sbool_vector_p, 1, 1, 0, "Return t if OBJECT is a bool-vector.")
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  (object)
     Lisp_Object object;
{
  if (BOOL_VECTOR_P (object))
    return Qt;
  return Qnil;
}

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DEFUN ("arrayp", Farrayp, Sarrayp, 1, 1, 0, "Return t if OBJECT is an array (string or vector).")
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  (object)
     Lisp_Object object;
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{
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  if (VECTORP (object) || STRINGP (object)
      || CHAR_TABLE_P (object) || BOOL_VECTOR_P (object))
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    return Qt;
  return Qnil;
}

DEFUN ("sequencep", Fsequencep, Ssequencep, 1, 1, 0,
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  "Return t if OBJECT is a sequence (list or array).")
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  (object)
     register Lisp_Object object;
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{
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  if (CONSP (object) || NILP (object) || VECTORP (object) || STRINGP (object)
      || CHAR_TABLE_P (object) || BOOL_VECTOR_P (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("bufferp", Fbufferp, Sbufferp, 1, 1, 0, "Return t if OBJECT is an editor buffer.")
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  (object)
     Lisp_Object object;
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{
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  if (BUFFERP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("markerp", Fmarkerp, Smarkerp, 1, 1, 0, "Return t if OBJECT is a marker (editor pointer).")
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  (object)
     Lisp_Object object;
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{
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  if (MARKERP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("subrp", Fsubrp, Ssubrp, 1, 1, 0, "Return t if OBJECT is a built-in function.")
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  (object)
     Lisp_Object object;
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{
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  if (SUBRP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("byte-code-function-p", Fbyte_code_function_p, Sbyte_code_function_p,
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       1, 1, 0, "Return t if OBJECT is a byte-compiled function object.")
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  (object)
     Lisp_Object object;
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{
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  if (COMPILEDP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("char-or-string-p", Fchar_or_string_p, Schar_or_string_p, 1, 1, 0,
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  "Return t if OBJECT is a character (an integer) or a string.")
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  (object)
     register Lisp_Object object;
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{
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  if (INTEGERP (object) || STRINGP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("integerp", Fintegerp, Sintegerp, 1, 1, 0, "Return t if OBJECT is an integer.")
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  (object)
     Lisp_Object object;
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{
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  if (INTEGERP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("integer-or-marker-p", Finteger_or_marker_p, Sinteger_or_marker_p, 1, 1, 0,
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  "Return t if OBJECT is an integer or a marker (editor pointer).")
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  (object)
     register Lisp_Object object;
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{
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  if (MARKERP (object) || INTEGERP (object))
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    return Qt;
  return Qnil;
}

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DEFUN ("natnump", Fnatnump, Snatnump, 1, 1, 0,
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  "Return t if OBJECT is a nonnegative integer.")
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  (object)
     Lisp_Object object;
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{
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  if (NATNUMP (object))
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    return Qt;
  return Qnil;
}

DEFUN ("numberp", Fnumberp, Snumberp, 1, 1, 0,
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       "Return t if OBJECT is a number (floating point or integer).")
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  (object)
     Lisp_Object object;
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{
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  if (NUMBERP (object))
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    return Qt;
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  else
    return Qnil;
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}

DEFUN ("number-or-marker-p", Fnumber_or_marker_p,
       Snumber_or_marker_p, 1, 1, 0,
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       "Return t if OBJECT is a number or a marker.")
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  (object)
     Lisp_Object object;
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{
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  if (NUMBERP (object) || MARKERP (object))
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    return Qt;
  return Qnil;
}
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DEFUN ("floatp", Ffloatp, Sfloatp, 1, 1, 0,
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       "Return t if OBJECT is a floating point number.")
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  (object)
     Lisp_Object object;
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{
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  if (FLOATP (object))
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    return Qt;
  return Qnil;
}
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/* Extract and set components of lists */

DEFUN ("car", Fcar, Scar, 1, 1, 0,
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  "Return the car of LIST.  If arg is nil, return nil.\n\
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Error if arg is not nil and not a cons cell.  See also `car-safe'.")
  (list)
     register Lisp_Object list;
{
  while (1)
    {
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      if (CONSP (list))
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	return XCAR (list);
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      else if (EQ (list, Qnil))
	return Qnil;
      else
	list = wrong_type_argument (Qlistp, list);
    }
}

DEFUN ("car-safe", Fcar_safe, Scar_safe, 1, 1, 0,
  "Return the car of OBJECT if it is a cons cell, or else nil.")
  (object)
     Lisp_Object object;
{
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  if (CONSP (object))
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    return XCAR (object);
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  else
    return Qnil;
}

DEFUN ("cdr", Fcdr, Scdr, 1, 1, 0,
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  "Return the cdr of LIST.  If arg is nil, return nil.\n\
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Error if arg is not nil and not a cons cell.  See also `cdr-safe'.")

  (list)
     register Lisp_Object list;
{
  while (1)
    {
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      if (CONSP (list))
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	return XCDR (list);
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      else if (EQ (list, Qnil))
	return Qnil;
      else
	list = wrong_type_argument (Qlistp, list);
    }
}

DEFUN ("cdr-safe", Fcdr_safe, Scdr_safe, 1, 1, 0,
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  "Return the cdr of OBJECT if it is a cons cell, or else nil.")
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  (object)
     Lisp_Object object;
{
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  if (CONSP (object))
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    return XCDR (object);
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  else
    return Qnil;
}

DEFUN ("setcar", Fsetcar, Ssetcar, 2, 2, 0,
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  "Set the car of CELL to be NEWCAR.  Returns NEWCAR.")
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  (cell, newcar)
     register Lisp_Object cell, newcar;
{
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  if (!CONSP (cell))
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    cell = wrong_type_argument (Qconsp, cell);

  CHECK_IMPURE (cell);
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  XCAR (cell) = newcar;
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  return newcar;
}

DEFUN ("setcdr", Fsetcdr, Ssetcdr, 2, 2, 0,
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  "Set the cdr of CELL to be NEWCDR.  Returns NEWCDR.")
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  (cell, newcdr)
     register Lisp_Object cell, newcdr;
{
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  if (!CONSP (cell))
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    cell = wrong_type_argument (Qconsp, cell);

  CHECK_IMPURE (cell);
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  XCDR (cell) = newcdr;
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  return newcdr;
}

/* Extract and set components of symbols */

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DEFUN ("boundp", Fboundp, Sboundp, 1, 1, 0, "Return t if SYMBOL's value is not void.")
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  (symbol)
     register Lisp_Object symbol;
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{
  Lisp_Object valcontents;
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  CHECK_SYMBOL (symbol, 0);
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  valcontents = SYMBOL_VALUE (symbol);
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  if (BUFFER_LOCAL_VALUEP (valcontents)
      || SOME_BUFFER_LOCAL_VALUEP (valcontents))
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    valcontents = swap_in_symval_forwarding (symbol, valcontents);
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  return (EQ (valcontents, Qunbound) ? Qnil : Qt);
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}

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DEFUN ("fboundp", Ffboundp, Sfboundp, 1, 1, 0, "Return t if SYMBOL's function definition is not void.")
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  (symbol)
     register Lisp_Object symbol;
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{
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  CHECK_SYMBOL (symbol, 0);
  return (EQ (XSYMBOL (symbol)->function, Qunbound) ? Qnil : Qt);
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}

DEFUN ("makunbound", Fmakunbound, Smakunbound, 1, 1, 0, "Make SYMBOL's value be void.")
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  (symbol)
     register Lisp_Object symbol;
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{
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  CHECK_SYMBOL (symbol, 0);
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  if (XSYMBOL (symbol)->constant)
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    return Fsignal (Qsetting_constant, Fcons (symbol, Qnil));
  Fset (symbol, Qunbound);
  return symbol;
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}

DEFUN ("fmakunbound", Ffmakunbound, Sfmakunbound, 1, 1, 0, "Make SYMBOL's function definition be void.")
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  (symbol)
     register Lisp_Object symbol;
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{
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  CHECK_SYMBOL (symbol, 0);
  if (NILP (symbol) || EQ (symbol, Qt))
    return Fsignal (Qsetting_constant, Fcons (symbol, Qnil));
  XSYMBOL (symbol)->function = Qunbound;
  return symbol;
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}

DEFUN ("symbol-function", Fsymbol_function, Ssymbol_function, 1, 1, 0,
  "Return SYMBOL's function definition.  Error if that is void.")
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  (symbol)
     register Lisp_Object symbol;
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{
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  CHECK_SYMBOL (symbol, 0);
  if (EQ (XSYMBOL (symbol)->function, Qunbound))
    return Fsignal (Qvoid_function, Fcons (symbol, Qnil));
  return XSYMBOL (symbol)->function;
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}

DEFUN ("symbol-plist", Fsymbol_plist, Ssymbol_plist, 1, 1, 0, "Return SYMBOL's property list.")
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  (symbol)
     register Lisp_Object symbol;
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{
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  CHECK_SYMBOL (symbol, 0);
  return XSYMBOL (symbol)->plist;
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}

DEFUN ("symbol-name", Fsymbol_name, Ssymbol_name, 1, 1, 0, "Return SYMBOL's name, a string.")
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  (symbol)
     register Lisp_Object symbol;
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{
  register Lisp_Object name;

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  CHECK_SYMBOL (symbol, 0);
  XSETSTRING (name, XSYMBOL (symbol)->name);
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  return name;
}

DEFUN ("fset", Ffset, Sfset, 2, 2, 0,
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  "Set SYMBOL's function definition to DEFINITION, and return DEFINITION.")
  (symbol, definition)
     register Lisp_Object symbol, definition;
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{
  CHECK_SYMBOL (symbol, 0);
  if (NILP (symbol) || EQ (symbol, Qt))
    return Fsignal (Qsetting_constant, Fcons (symbol, Qnil));
  if (!NILP (Vautoload_queue) && !EQ (XSYMBOL (symbol)->function, Qunbound))
    Vautoload_queue = Fcons (Fcons (symbol, XSYMBOL (symbol)->function),
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			     Vautoload_queue);
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  XSYMBOL (symbol)->function = definition;
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  /* Handle automatic advice activation */
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  if (CONSP (XSYMBOL (symbol)->plist) && !NILP (Fget (symbol, Qad_advice_info)))
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    {
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      call2 (Qad_activate_internal, symbol, Qnil);
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      definition = XSYMBOL (symbol)->function;
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    }
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  return definition;
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}

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DEFUN ("defalias", Fdefalias, Sdefalias, 2, 2, 0,
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  "Set SYMBOL's function definition to DEFINITION, and return DEFINITION.\n\
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Associates the function with the current load file, if any.")
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  (symbol, definition)
     register Lisp_Object symbol, definition;
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{
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  definition = Ffset (symbol, definition);
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  LOADHIST_ATTACH (symbol);
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  return definition;
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}

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DEFUN ("setplist", Fsetplist, Ssetplist, 2, 2, 0,
  "Set SYMBOL's property list to NEWVAL, and return NEWVAL.")
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  (symbol, newplist)
     register Lisp_Object symbol, newplist;
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{
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  CHECK_SYMBOL (symbol, 0);
  XSYMBOL (symbol)->plist = newplist;
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  return newplist;
}
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DEFUN ("subr-arity", Fsubr_arity, Ssubr_arity, 1, 1, 0,
  "Return minimum and maximum number of args allowed for SUBR.\n\
SUBR must be a built-in function.\n\
The returned value is a pair (MIN . MAX).  MIN is the minimum number\n\
of args.  MAX is the maximum number or the symbol `many', for a\n\
function with `&rest' args, or `unevalled' for a special form.")
  (subr)
     Lisp_Object subr;
{
  short minargs, maxargs;
  if (!SUBRP (subr))
    wrong_type_argument (Qsubrp, subr);
  minargs = XSUBR (subr)->min_args;
  maxargs = XSUBR (subr)->max_args;
  if (maxargs == MANY)
    return Fcons (make_number (minargs), Qmany);
  else if (maxargs == UNEVALLED)
    return Fcons (make_number (minargs), Qunevalled);
  else
    return Fcons (make_number (minargs), make_number (maxargs));
}

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DEFUN ("subr-interactive-form", Fsubr_interactive_form, Ssubr_interactive_form, 1, 1, 0,
  "Return the interactive form of SUBR or nil if none.\n\
SUBR must be a built-in function.  Value, if non-nil, is a list\n\
\(interactive SPEC).")
  (subr)
     Lisp_Object subr;
{
  if (!SUBRP (subr))
    wrong_type_argument (Qsubrp, subr);
  if (XSUBR (subr)->prompt)
    return list2 (Qinteractive, build_string (XSUBR (subr)->prompt));
  return Qnil;
}

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758

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/***********************************************************************
		Getting and Setting Values of Symbols
 ***********************************************************************/

/* Return the symbol holding SYMBOL's value.  Signal
   `cyclic-variable-indirection' if SYMBOL's chain of variable
   indirections contains a loop.  */

Lisp_Object
indirect_variable (symbol)
     Lisp_Object symbol;
{
  Lisp_Object tortoise, hare;

  hare = tortoise = symbol;

  while (XSYMBOL (hare)->indirect_variable)
    {
      hare = XSYMBOL (hare)->value;
      if (!XSYMBOL (hare)->indirect_variable)
	break;
      
      hare = XSYMBOL (hare)->value;
      tortoise = XSYMBOL (tortoise)->value;

      if (EQ (hare, tortoise))
	Fsignal (Qcyclic_variable_indirection, Fcons (symbol, Qnil));
    }

  return hare;
}


DEFUN ("indirect-variable", Findirect_variable, Sindirect_variable, 1, 1, 0,
  "Return the variable at the end of OBJECT's variable chain.\n\
If OBJECT is a symbol, follow all variable indirections and return the final\n\
variable.  If OBJECT is not a symbol, just return it.\n\
Signal a cyclic-variable-indirection error if there is a loop in the\n\
variable chain of symbols.")
  (object)
     Lisp_Object object;
{
  if (SYMBOLP (object))
    object = indirect_variable (object);
  return object;
}

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/* Given the raw contents of a symbol value cell,
   return the Lisp value of the symbol.
   This does not handle buffer-local variables; use
   swap_in_symval_forwarding for that.  */

Lisp_Object
do_symval_forwarding (valcontents)
     register Lisp_Object valcontents;
{
  register Lisp_Object val;
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  int offset;
  if (MISCP (valcontents))
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    switch (XMISCTYPE (valcontents))
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      {
      case Lisp_Misc_Intfwd:
	XSETINT (val, *XINTFWD (valcontents)->intvar);
	return val;
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      case Lisp_Misc_Boolfwd:
	return (*XBOOLFWD (valcontents)->boolvar ? Qt : Qnil);
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      case Lisp_Misc_Objfwd:
	return *XOBJFWD (valcontents)->objvar;
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      case Lisp_Misc_Buffer_Objfwd:
	offset = XBUFFER_OBJFWD (valcontents)->offset;
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	return PER_BUFFER_VALUE (current_buffer, offset);
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      case Lisp_Misc_Kboard_Objfwd:
	offset = XKBOARD_OBJFWD (valcontents)->offset;
	return *(Lisp_Object *)(offset + (char *)current_kboard);
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      }
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  return valcontents;
}

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/* Store NEWVAL into SYMBOL, where VALCONTENTS is found in the value cell
   of SYMBOL.  If SYMBOL is buffer-local, VALCONTENTS should be the
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   buffer-independent contents of the value cell: forwarded just one
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   step past the buffer-localness.

   BUF non-zero means set the value in buffer BUF instead of the
   current buffer.  This only plays a role for per-buffer variables.  */
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void
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store_symval_forwarding (symbol, valcontents, newval, buf)
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     Lisp_Object symbol;
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     register Lisp_Object valcontents, newval;
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     struct buffer *buf;
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{
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  switch (SWITCH_ENUM_CAST (XTYPE (valcontents)))
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    {
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    case Lisp_Misc:
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      switch (XMISCTYPE (valcontents))
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	{
	case Lisp_Misc_Intfwd:
	  CHECK_NUMBER (newval, 1);
	  *XINTFWD (valcontents)->intvar = XINT (newval);
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	  if (*XINTFWD (valcontents)->intvar != XINT (newval))
	    error ("Value out of range for variable `%s'",
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		   XSYMBOL (symbol)->name->data);
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	  break;

	case Lisp_Misc_Boolfwd:
	  *XBOOLFWD (valcontents)->boolvar = NILP (newval) ? 0 : 1;
	  break;

	case Lisp_Misc_Objfwd:
	  *XOBJFWD (valcontents)->objvar = newval;
	  break;

	case Lisp_Misc_Buffer_Objfwd:
	  {
	    int offset = XBUFFER_OBJFWD (valcontents)->offset;
	    Lisp_Object type;

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	    type = PER_BUFFER_TYPE (offset);
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	    if (XINT (type) == -1)
	      error ("Variable %s is read-only", XSYMBOL (symbol)->name->data);

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	    if (! NILP (type) && ! NILP (newval)
		&& XTYPE (newval) != XINT (type))
	      buffer_slot_type_mismatch (offset);

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	    if (buf == NULL)
	      buf = current_buffer;
	    PER_BUFFER_VALUE (buf, offset) = newval;
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	  }
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	  break;

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	case Lisp_Misc_Kboard_Objfwd:
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	  {
	    char *base = (char *) current_kboard;
	    char *p = base + XKBOARD_OBJFWD (valcontents)->offset;
	    *(Lisp_Object *) p = newval;
	  }
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	  break;

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	default:
	  goto def;
	}
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      break;

    default:
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    def:
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      valcontents = SYMBOL_VALUE (symbol);
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      if (BUFFER_LOCAL_VALUEP (valcontents)
	  || SOME_BUFFER_LOCAL_VALUEP (valcontents))
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	XBUFFER_LOCAL_VALUE (valcontents)->realvalue = newval;
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      else
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	SET_SYMBOL_VALUE (symbol, newval);
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    }
}

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/* Set up SYMBOL to refer to its global binding.
   This makes it safe to alter the status of other bindings.  */

void
swap_in_global_binding (symbol)
     Lisp_Object symbol;
{
  Lisp_Object valcontents, cdr;
  
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  valcontents = SYMBOL_VALUE (symbol);
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  if (!BUFFER_LOCAL_VALUEP (valcontents)
      && !SOME_BUFFER_LOCAL_VALUEP (valcontents))
    abort ();
  cdr = XBUFFER_LOCAL_VALUE (valcontents)->cdr;

  /* Unload the previously loaded binding.  */
  Fsetcdr (XCAR (cdr),
	   do_symval_forwarding (XBUFFER_LOCAL_VALUE (valcontents)->realvalue));
  
  /* Select the global binding in the symbol.  */
  XCAR (cdr) = cdr;
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  store_symval_forwarding (symbol, valcontents, XCDR (cdr), NULL);
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  /* Indicate that the global binding is set up now.  */
  XBUFFER_LOCAL_VALUE (valcontents)->frame = Qnil;
  XBUFFER_LOCAL_VALUE (valcontents)->buffer = Qnil;
  XBUFFER_LOCAL_VALUE (valcontents)->found_for_frame = 0;
  XBUFFER_LOCAL_VALUE (valcontents)->found_for_buffer = 0;
}

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/* Set up the buffer-local symbol SYMBOL for validity in the current buffer.
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   VALCONTENTS is the contents of its value cell,
   which points to a struct Lisp_Buffer_Local_Value.

   Return the value forwarded one step past the buffer-local stage.
   This could be another forwarding pointer.  */
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static Lisp_Object
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swap_in_symval_forwarding (symbol, valcontents)
     Lisp_Object symbol, valcontents;
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{
  register Lisp_Object tem1;
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  tem1 = XBUFFER_LOCAL_VALUE (valcontents)->buffer;
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  if (NILP (tem1)
      || current_buffer != XBUFFER (tem1)
      || (XBUFFER_LOCAL_VALUE (valcontents)->check_frame
	  && ! EQ (selected_frame, XBUFFER_LOCAL_VALUE (valcontents)->frame)))
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    {
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      if (XSYMBOL (symbol)->indirect_variable)
	symbol = indirect_variable (symbol);
      
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      /* Unload the previously loaded binding.  */
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      tem1 = XCAR (XBUFFER_LOCAL_VALUE (valcontents)->cdr);
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      Fsetcdr (tem1,
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	       do_symval_forwarding (XBUFFER_LOCAL_VALUE (valcontents)->realvalue));
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      /* Choose the new binding.  */
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      tem1 = assq_no_quit (symbol, current_buffer->local_var_alist);
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      XBUFFER_LOCAL_VALUE (valcontents)->found_for_frame = 0;
      XBUFFER_LOCAL_VALUE (valcontents)->found_for_buffer = 0;
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      if (NILP (tem1))
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	{
	  if (XBUFFER_LOCAL_VALUE (valcontents)->check_frame)
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	    tem1 = assq_no_quit (symbol, XFRAME (selected_frame)->param_alist);
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	  if (! NILP (tem1))
	    XBUFFER_LOCAL_VALUE (valcontents)->found_for_frame = 1;
	  else
	    tem1 = XBUFFER_LOCAL_VALUE (valcontents)->cdr;
	}
      else
	XBUFFER_LOCAL_VALUE (valcontents)->found_for_buffer = 1;

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      /* Load the new binding.  */
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      XCAR (XBUFFER_LOCAL_VALUE (valcontents)->cdr) = tem1;
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      XSETBUFFER (XBUFFER_LOCAL_VALUE (valcontents)->buffer, current_buffer);
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      XBUFFER_LOCAL_VALUE (valcontents)->frame = selected_frame;
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      store_symval_forwarding (symbol,
			       XBUFFER_LOCAL_VALUE (valcontents)->realvalue,
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			       Fcdr (tem1), NULL);
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    }
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  return XBUFFER_LOCAL_VALUE (valcontents)->realvalue;
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}

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/* Find the value of a symbol, returning Qunbound if it's not bound.
   This is helpful for code which just wants to get a variable's value
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   if it has one, without signaling an error.
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   Note that it must not be possible to quit
   within this function.  Great care is required for this.  */
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Lisp_Object
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find_symbol_value (symbol)
     Lisp_Object symbol;
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{
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  register Lisp_Object valcontents;
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  register Lisp_Object val;
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  CHECK_SYMBOL (symbol, 0);
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  valcontents = SYMBOL_VALUE (symbol);
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  if (BUFFER_LOCAL_VALUEP (valcontents)
      || SOME_BUFFER_LOCAL_VALUEP (valcontents))
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    valcontents = swap_in_symval_forwarding (symbol, valcontents);
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  if (MISCP (valcontents))
    {
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      switch (XMISCTYPE (valcontents))
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	{
	case Lisp_Misc_Intfwd:
	  XSETINT (val, *XINTFWD (valcontents)->intvar);
	  return val;
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	case Lisp_Misc_Boolfwd:
	  return (*XBOOLFWD (valcontents)->boolvar ? Qt : Qnil);
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	case Lisp_Misc_Objfwd:
	  return *XOBJFWD (valcontents)->objvar;
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	case Lisp_Misc_Buffer_Objfwd:
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